1. Field of the Invention
The present invention relates generally to pectin-containing compositions and processes for their production. In particular, the present invention relates to a process for preparing pecto-cellulosic compositions from whole citrus peel.
Pectin is a natural colloid, frequently found in the plant world as a component of cell walls, where together with other components, such as hemicelluloses, it is linked to the cellulose and constitutes both the structural tissue and the "cement" which gives rigidity to plant cells. Pectin is present in all plant tissue, such as in apples and citrus fruits, in variable quantities, as well as in some roots (beets, carrots), tubers (potatoes), in sunflower heads, and elsewhere. Pectin has long been used in the home for gelling jams using, for example, apple core or quinces as the pectin source. Today, the fruit and confectionery industry has used pectin widely for its gelling properties in acid and sugar media. Other pectin properties, such as its gelling action in less acidic medium and in the presence of calcium, thickening, colloidal suspension, protection of casein, and the like, also contribute to the role of pectin in the manufacture of food and pharmaceutical products.
Most commercially available pectins are purified to about 70% to 80% by weight polyanhydrogalacturonic acid (AGA) and have a varying degree of methoxylation (DM). High methoxyl pectins (DM above about 50%) form gels at pH values below about 3.5 in the presence of sugar levels above about 60%. High DM pectins are typically used for gelling preserves and confectionery foods. Low methoxyl pectins (DM between about 20% and 50%) form gels at wider pH ranges in the absence of sugars, but require the presence of divalent cations.
Commercial pectin is obtained from starting materials having a much lower AGA content, such as dried citrus peel having an AGA content in the range from about 20% to 30%. Extraction is achieved by hydrolysis, in warm acidic medium, of protopectin to release the potentially soluble pectinic acids from the cellulosic matrix in which they are initially included. After separation of the cellulosic components, pectin is precipitated from the resulting pectic juices, typically using an alcohol. The resulting fibrous coagulum is alcohol washed, squeezed, vacuum dried, and then ground in order to obtain a fine powder. The separated cellulose is a low volume by-product which can be used, for example, as an animal feed bulking agent.
Thus, it can be seen that the present method for producing commercial pectin products can be expensive, both in capital expenditures and in operating costs. Moreover, the present methods utilize only a portion of the starting materials and result in waste or low value usage of the cellulosic portions of the starting material.
For these reasons, it would be desirable to provide less costly methods and processes for producing pectin compositions from starting materials, such as whole citrus peels. Preferably, the methods could be implemented with reduced capital expenditures (e.g., by requiring fewer processing steps) and operating costs (e.g., by operating at ambient temperature). It would be further desirable if the methods were able to incorporate a significant percentage of the cellulose in the starting material in the final product. Cellulose is an important part of dietary fiber and incorporation of the final product would further enhance the economics of the method.
2. Description of the Background Art
East German Patent Application No. 258743 (Abstract) describes the production of a pectin-like material for use with comminuted meats. The pectin-containing material is produced from vegetables by comminution, followed by acidification, neutralization, and mechanical dehydration. U.S. Pat. Nos. 4,923,981 and 4,831,127, relate to the preparation of "parenchymal cell" cellulose from pectin-containing materials, such as sugar beet and citrus pulp. The materials are first treated with a strong acid or a strong base at high temperatures for short periods of time to release the cellulosic and hemi-cellulosic components thereof. The treatment releases pectin from the starting materials without substantial degradation. The starting material is subjected to physical shearing, and the solid and liquid fractions of the treated mixture are separated and utilized separately. U.S. Pat. No. 4,143,172 teaches the use of comminuted citrus peel as a pectin material. U.S. Pat. No. 3,982,003, similarly teaches the preparation of the pectin-like material by comminution of citrus pulp, where the pulp is treated with a mild base in order to reduce the degree of esterification. U.S. Pat. No. 2,452,750 teaches methods for producing pectin by soaking comminuted citrus peel in a reagent which is a nonsolvent for pectinous substances. U.S. Pat. No. 2,132,065, describes hugh temperature, alkaline separation of pectin from citrus peel. U.S. Pat. No. 2,022,471 discloses a process for making pectous materials using a filter aid such as diatomaceous earth. International application, Pub. No. WO 91/15517, describes methods for producing pectin-containing products. British patent 1,369,198 describes a process for preparing simulated fruit using a pectate sol. British patent 1,508,993 is related to U.S. Pat. Nos. 3,982,003 and 4,143,172, described above.
The descriptions in each of the above references are incorporated herein by reference.